Microcalcification Acts as a Stress and Stretch Amplifier in the Coronary Atherosclerotic Plaque Affecting Its Vulnerability: An IVUS-Based Finite Element Study

2012 ◽  
Author(s):  
Yuan Huang ◽  
Wenkai Wang ◽  
Zhongzhao Teng ◽  
Daniel R. Obaid ◽  
Jing He ◽  
...  
Keyword(s):  
Finite Element ◽  
Plaque Rupture ◽  
High Stress ◽  
Material Strength ◽  
Stress Concentrations ◽  
Mortality And Morbidity ◽  
High Stress Concentration ◽  
Fibrous Cap ◽  
High Stress Level ◽  
Rupture Site

Atherosclerotic disease remains a leading cause of mortality and morbidity worldwide despite significant advances in its management (1). Atherosclerosis, characterized by plaque consisting a lipid-rich necrotic core encapsulated in a fibrous cap, may result in plaque rupture and subsequently cause acute ischaemic events such as myocardial infarction and stroke. Under physiological conditions, plaque is subjected to mechanical loading due to blood pressure and flow and rupture possibly occurs if these extra loadings exceed the material strength of the fibrous cap (2–4). This hypothesis has been indirectly validated by the combination of histological examination and finite element simulations that the rupture site often bears a high stress concentration either in carotid (3, 5, 6) or coronary (2) plaques. It has been noted that most rupture sites are located at the shoulder region (2), where the curvature is locally large (4) leading to a high stress level (7). However, the rupture site does not always coincide with the site where high stress concentrations appear and about thirty to forty percent of ruptures occur in the middle region where the calculated stress is relatively low (2, 8). This demonstrates the limitations of current approaches.

scholarly journals Coronary plaque composition influences biomechanical stress and predicts plaque rupture in a morpho-mechanic OCT analysis

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Andrea Milzi ◽  
Enrico Domenico Lemma ◽  
Rosalia Dettori ◽  
Kathrin Burgmaier ◽  
Nikolaus Marx ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Vessel Wall ◽  
Plaque Rupture ◽  
Area Under The Curve ◽  
Stress Concentrations ◽  
Element Analysis ◽  
Biomechanical Stress ◽  
Fibrous Cap ◽  
Maximal Stress

Plaque rupture occurs if stress within coronary lesions exceeds the protection exerted by the fibrous cap overlying the necrotic lipid core. However, very little is known about the biomechanical stress exerting this disrupting force. Employing optical coherence tomography (OCT), we generated plaque models and performed finite-element analysis to simulate stress distributions within the vessel wall in 10 ruptured and 10 non-ruptured lesions. In ruptured lesions, maximal stress within fibrous cap (peak cap stress [PCS]: 174 ± 67 vs. 52 ± 42 kPa, p<0.001) and vessel wall (maximal plaque stress [MPS]: 399 ± 233 vs. 90 ± 95 kPa, p=0.001) were significantly higher compared to non-ruptured plaques. Ruptures arose in the immediate proximity of maximal stress concentrations (angular distances: 21.8 ± 30.3° for PCS vs. 20.7 ± 23.7° for MPS); stress concentrations excellently predicted plaque rupture (area under the curve: 0.940 for PCS, 0.950 for MPS). This prediction of plaque rupture was superior to established vulnerability features such as fibrous cap thickness or macrophage infiltration. In conclusion, OCT-based finite-element analysis effectively assesses plaque biomechanics, which in turn predicts plaque rupture in patients. This highlights the importance of morpho-mechanic analysis assessing the disrupting effects of plaque stress.

A New Shaft Coupling Design for a High-Speed Rotor Wheel

1995 ◽  
Author(s):  
Tibor Kiss ◽  
Wing-Fai Ng ◽  
Larry D. Mitchell
Keyword(s):  
High Speed ◽  
High Stress ◽  
Critical Issue ◽  
Working Environment ◽  
Outer Diameter ◽  
Stress Concentrations ◽  
Coupling Region ◽  
Rotor Wheel ◽  
High Stress Concentration ◽  
Safety Margins

Abstract A high-speed rotor wheel for a wind-tunnel experiment has been designed. The rotor wheel was similar to one in an axial turbine, except that slender bars replaced the blades. The main parameters of the rotor wheel were an outer diameter of 10“, a maximum rotational speed of 24,000 RPM and a maximum transferred torque of 64 lb-ft. Due to the working environment, the rotor had to be designed with high safety margins. The coupling of the rotor wheel with the shaft was found to be the most critical issue, because of the high stress concentration factors associated with the conventional coupling methods. The efforts to reduce the stress concentrations resulted in an advanced coupling design which is the main subject of the present paper. This new design was a special key coupling in which six dowel pins were used for keys. The key slots, now pin-grooves, were placed in bosses on the inner surface of the hub. The hub of the rotor wheel was relatively long, which allowed for applying the coupling near the end faces of the hub, that is, away from the highly loaded centerplane. The long hub resulted in low radial expansion in the coupling region. Therefore, solid contact between the shaft and the hub could be maintained for all working conditions. To develop and verify the design ideas, stress and deformation analyses were carried out using quasi-two-dimensional finite element models. An overall safety factor of 3.7 resulted. The rotor has been built and successfully accelerated over the design speed in a spin test pit.

Stresses in a composite material with a single broken fibre

1967 ◽  
Vol 2 (3) ◽  
pp. 239-245 ◽  
Author(s):  
M J Iremonger ◽  
W G Wood
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Composite Material ◽  
Composite Materials ◽  
High Stress ◽  
The Finite Element Method ◽  
Stress Concentrations ◽  
Lower Stress ◽  
Fibre Break ◽  
Matrix Yielding

An investigation has been made into the suitability of the finite-element method for studying the stresses in composite materials and the case of a single broken fibre in a matrix has been examined. It has been found that high stress concentrations occur in the region of the fibre break which increase with decreasing end gap and would cause matrix yielding or fracture at comparatively low overall stresses. When the end gap is not void but filled with matrix much lower stress concentrations occur which, below a certain value of end gap, actually decrease as the gap is made smaller.

Finite Element Analysis of Residual Stresses in Threaded End Closures

1991 ◽  
Vol 113 (3) ◽  
pp. 398-401 ◽  
Author(s):  
A. Chaaban ◽  
U. Muzzo
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Bauschinger Effect ◽  
High Stress ◽  
Empirical Method ◽  
Pressure Vessels ◽  
Element Analysis ◽  
High Stress Concentration ◽  
Proof Testing ◽  
Pressure Cycle

Due to the high stress concentration at the root of the first active thread in threaded end closures of high pressure vessels, yielding may occur in this region during the application of the first pressure cycle or proof testing. This overstraining introduces residual stresses that influence the fatigue performance of the vessel. This paper presents a parametric analysis of threaded end closures using elastic and elasto-plastic finite element solutions. The results are used to discuss the influence of these residuals on the estimated fatigue life when the vessel is subjected to repeated internal pressure. A simple empirical method to allow for the Bauschinger effect of the material is also proposed.

On the Axisymmetric Response of a Damaged Flexible Pipe

2014 ◽  
Author(s):  
José Renato M. de Sousa ◽  
Carlos Magluta ◽  
Ney Roitman ◽  
George C. Campello
Keyword(s):  
Finite Element ◽  
Analytical Model ◽  
Load Capacity ◽  
High Stress ◽  
Experimental Tests ◽  
Theoretical Models ◽  
Experimental Measurements ◽  
Fe Model ◽  
Flexible Pipe ◽  
High Stress Concentration

This work focuses on the structural analysis of a damaged 9.13″ flexible pipe to pure and combined axisymmetric loads. A set of experimental tests was carried out considering one up to ten broken wires in the outer tensile armor of the pipe and the results obtained are compared to those provided by a previously presented finite element (FE) model and a traditional analytical model. In the experimental tests, the pipe was firstly subjected to pure tension and, then, the responses to clockwise and anti-clockwise torsion superimposed with tension were investigated. In these tests, the induced strains in the outer armor were measured. Moreover, the axial elongation of the pipe was monitored when the pipe is subjected to tension, whilst the twist of the pipe was measured when torsion is imposed. The experimental results pointed to a slight decrease in the stiffness of the pipe with the increasing number of broken wires and, furthermore, a redistribution of forces among the intact wires of the damaged layer with high stress concentration in the wires close to the damaged ones. Both theoretical models captured these features, but, while the results obtained with the FE model agreed well with the experimental measurements, the traditional analytical model presented non-conservative results. Finally, the results obtained are employed to estimate the load capacity of the pipe.

Histology-Based, Lesion-Specific Modeling of Stress Differences Between Plaque Rupture and Plaque Erosion

2011 ◽  
Author(s):  
Ian C. Campbell ◽  
Renu Virmani ◽  
John N. Oshinski ◽  
W. Robert Taylor
Keyword(s):  
Finite Element ◽  
Plaque Rupture ◽  
Solid Wall ◽  
Element Model ◽  
Blood Pool ◽  
Future Studies ◽  
Fibrous Cap ◽  
Plaque Disruption ◽  
Plaque Erosion ◽  
Specific Modeling

Plaque erosion is a cause of thrombosis wherein a thrombus forms over an atherosclerotic plaque without any disruption of the fibrous cap. This is in contrast to plaque rupture, traditionally considered the main cause of atherosclerosis-related thrombosis and frequently studied in biomechanics, wherein the fibrous cap becomes disrupted and exposes the lipid core of the plaque to the blood pool. Also unlike plaque rupture, plaque erosion has been observed to happen most frequently in women [1]. Despite identification, the cause of plaque erosion remains unknown and has been virtually unstudied from a biomechanical perspective. In this study, we employ a unique high-resolution, histology-based finite element model of solid wall stresses to investigate biomechanical differences between plaque rupture and plaque erosion. In future studies, this computed stress distribution can be correlated to expression of biomarkers related to the plaque disruption process in order to investigate the cause of plaque erosion.

Finite Element Stress Analysis of Composite Sucker Rods

2003 ◽  
Vol 125 (4) ◽  
pp. 299-303 ◽  
Author(s):  
Eyassu Woldesenbet
Keyword(s):  
Finite Element ◽  
High Stress ◽  
Experimental Tests ◽  
Fatigue Loading ◽  
Stress Concentrations ◽  
Element Analysis ◽  
Composite Rod ◽  
Rod System ◽  
Sucker Rod ◽  
2D And 3D

Analysis of polymer-matrix composite sucker rod systems using finite element methods is performed. Composite sucker rods used in oil production fail mainly due to fatigue loading. In majority of cases, the failure is in the region of the joint where the composite rod and the steel endfitting meet. 2D and 3D Finite Element Analysis and experimental tests are carried out in order to observe the stress distribution and to find the regions of stress concentrations inside the endfitting. The causes of failure of the composite sucker rods are identified as high transverse compressive stress caused by overloading that results in the crushing of the rod, and high stress concentrations present at the grooves of the endfitting that initiate premature cracks. Based on the result of this study, enhanced design of the composite sucker rod system can be accomplished.

Stress Concentrations of Vulnerable Plaques With a Composite Variable Core

2010 ◽  
Author(s):  
Eyass Massarwa ◽  
Aronis Ze’ev ◽  
Rami Eliasy ◽  
Rami Haj-Ali ◽  
Shmuel Einav
Keyword(s):  
Plaque Rupture ◽  
Necrotic Core ◽  
Intraplaque Hemorrhage ◽  
Plaque Morphology ◽  
Rapid Progression ◽  
Stress Concentrations ◽  
Coronary Syndrome ◽  
Fibrous Cap ◽  
Vulnerable Plaques ◽  
Life Threatening

Vulnerable plaques are inflamed, active, and growing lesions which are prone to complications such as rupture, luminal and mural thrombosis, intraplaque hemorrhage, and rapid progression to stenosis. It remains difficult to assess what factors influence the biomechanical stability of vulnerable plaques and promote some of them to rupture while others remain intact. The rupture of thin fibrous cap overlying the necrotic core of a vulnerable plaque is the principal cause of acute coronary syndrome. The mechanism or mechanisms responsible for the sudden conversion of a stable atherosclerotic plaque to a life threatening athero-thrombotic lesion are not fully understood. It has been widely assumed that plaque morphology is the major determinant of clinical outcome [1, 2]. Thin-cap fibroatheroma with a large necrotic core and a fibrous cap of < 65μm was describes as a more specific precursor of plaque rupture due to tissue stress.

A study of the deformation and fracture of single-crystal gold films of high strength inside an electron microscope

1960 ◽  
Vol 255 (1281) ◽  
pp. 218-231 ◽  
Keyword(s):  
Plastic Deformation ◽  
Tensile Strength ◽  
Electron Microscope ◽  
Single Crystal ◽  
High Stress ◽  
High Strength ◽  
Gold Wire ◽  
Detailed Examination ◽  
Stress Concentrations ◽  
High Stress Level

Single-crystal films of gold in (111) orientation, and 500 to 2000 Å in thickness, have been prepared by an evaporation technique. A device has been constructed to allow these films to be strained in a controlled manner while under observation inside the electron microscope (Siemens Elmiskop I). It is shown, by the absence of observable plastic deformation, that the films deform elastically up to abnormally high strain values. This is confirmed, in the case of 500 Å films, by precision electron diffraction measurements, which indicate elastic strains as high as 1 to 1·5%. This represents a tensile strength several times that of hard-drawn gold wire. The high tensile strength occurs despite the presence of a high density of dislocations. Failure occurs once the elastic limit is exceeded. Detailed examination of the fractured specimens reveals that highly localized plastic deformation occurs immediately before fracture. The nature of the fracture process has been deduced from the micrographs, and it is shown that the catastrophic failure occurs as a result of the high stress level which exists when plastic deformation occurs, coupled with the stress concentrations which occur as localized thinning takes place.

Finite Element Study of the Effect of Canal Diameter on the Stress Distributions in Post-Core Restored Endodontically Treated Maxillary Incisor

2011 ◽  
Vol 110-116 ◽  
pp. 1519-1524
Author(s):  
Amir Kazemi ◽  
Vahid Khamesi ◽  
Sayad Hajimahamadi
Keyword(s):  
Finite Element ◽  
High Stress ◽  
Maxillary Incisor ◽  
Finite Element Models ◽  
Stress Distributions ◽  
Stress Concentrations ◽  
Static Loads ◽  
3D Finite Element ◽  
Apical Portion ◽  
Canal Diameter

In this study, 3D finite element models were developed to evaluate the effect of canal diameter on the stress distributions of post and dentin in post-core restored endodontically treated maxillary incisor under various static loads. The results show that the posts with large diameters support more of the load, but cause high stress concentrations at the apical portion of the root, which is not desirable.

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